The present invention relates to high power, high voltage systems for switching large currents, and more particularly to such systems employing plasma sources controlled by electron beams.
Electron Beam Controlled Switches (EBCS) have beem employed in high voltage, high power switching applications. Typically, prior art systems employ a switch with a thermionic cathode (at high temperature) with planar arrangement of the EBCS. It is understood by applicants that the Westinghouse Corporation has employed a Wire-Ion-Plasma Electron-gun (WIP E-gun) as the electron source with a planar arrangement of an EBCS. WIP E-gun are discussed, for example in U.S. Pat. Nos. 4,025,818 and 3,970,892, entitled "Wire Ion Plasma Electron Gun" and "Ion Plasma Electron Gun", respectively.
U.S. Pat. No. 4,063,130, "Low Impedance Electron Beam Controlled Discharge Switching Device" issued to Robert O. Hunter, Jr., discloses a switch comprising a gas discharge device and an electron gun with planar electrodes which may be circularly symmetrical about a common axis of rotation. However, the patent is not understood to disclose a WIP E-gun as the electron source. The cold cathode (over-voltage vacuum diode) electron gun described in the Hunter patent is understood to be operable primarily for pulsed operation, such that the switch could not be adapted to conduction of large currents for sustained periods. Further, to turn the electron beam "OFF", the voltage supply for the electron gun must be turned "OFF".
Various other problems are associated with the switches of the prior art. For example, thermionic devices require heater cathode power, a heater supply, a grid pulser operating at high voltage, and means for maintaining a sensitive high temperature cathode so that it remains active in a harsh environment. Thermonic cathodes require a very high vacuum environment and are easily contaminated. Field emitting cathodes, such as the Hunter device, operate only for short pulses. The known EBCS devices require a large active area to carry the typical switch currents, and the physical size of planar EBCS devices may be quite large. X-ray shielding is a major design and weight consideration in these EBCS prior art devices.
It is, therefore, an object of the present invention to provide an EBCS which is superior to other types of switches for many high power applications.
Another object of the invention is to provide a switch which is compact and highly efficient.
A further object is to provide an EBCS device which minimizes the required shielding of X-ray.
Yet another object of the invention is to provide a WIP E-gun having a radial geometry.
A further object of the invention is to provide a radial geometry EBCS employing a WIP E-gun as the electron source.
Another object of the invention is to provide a switch having the capability to turn "OFF" under load, i.e., against a high voltage.